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Weird Issue with Yamaha R-50

Theo A

Theo A

Active Member
Hello all, my next project is a Yamaha R-50. I am fixing it up for a family member, and when I first inspected the unit, the only issue seemed to be scratchy controls. As long as the buttons weren't moved, it sounded great. All I did was open up the receiver and find the very small holes on the top of the control pots and switches an gave it a good clean. I plug everything back in, and the only input that is giving any sound is the tuner, and even that is very anoemic sounding and quiet. No other inputs work, and I am extemely confused how a simple clean with deoxit could have done anything. What went wrong?
 
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avionic said:
Thats a waste of time and deoxit...;) Need to spray it into the pots from the solder pin connection opening.:thumbsup:
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Regardless of the right opening, how would that do anything negative to the receiver and make it completely silent except for the tuner input?
 
Theo A said:
I plug everything back in,
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It worked before and now it doesn't..Check solder connections on any sockets or plugs. Look for iffy solder connections.. Loose wires or components. Something got broke loose while you had it apart.
Theo A said:
Regardless of the right opening, how would that do anything negative to the receiver and make it completely silent except for the tuner input?
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Probably nothing..Unless over spray has shorted something..
Theo A said:
the only input that is giving any sound is the tuner,
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Points to the input selector switch...
 
Check the solder joints at the front of the main printed circuit board, for the pots and switches. The R-50 is vulnerable to solder joint failure there because of thermal effects associated with the controls being rigidly mounted to the main circuit board.

The main PCB is secured at the back of the unit with screws, and the front of the PCB is constrained by the solid mounting of the pots with coaxial nuts, to the front panel, which in turn is firmly screwed to the rest of the structure. So the PCB is not free to expand or contract fore and aft. Each time the receiver is turned on and warms, the board tries to expand, and each time it is turned off and cools, the board tries to contract. The thermal expansion/contraction results in cyclic mechanical forces, which are carried by the solder joints of the controls. This results in fatigue failure of the solder joints. You will probably find ring cracks on those solder joints, and the spray has probably exposed a faulty connection.The signal goes through the bass extension switch, bass, treble, balance, and volume pots, so bad solder joints there will stop it from working correctly.

I picked up a non-working R-50 awhile back to improve my tech skills, and it had this problem, plus others which were likely the result of someone fishing around to find the problem. It is working fine in my garage now. A nice little receiver - it's a Yamaha, after all. Although it uses an amplifier module instead of discrete parts, it has the coolest (pun) copper heat pipe to draw the heat from the amp module to the heat sink.
 
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Theo A, in addition to Arc de Triamp's suggestions, reflow your voltage regulators, too. Got a Yamaha R-30 receiver last summer off C-List. Seller said it worked last time he played it. Turned on, but that was it. After exploratory exam, noticed voltage regulators were loose. Also replaced replacement 5,600 uf snap-in power caps with radial 10,000 uf Nichicons. IC-amp chip now replicates guitar tones just as well as moi's Peavey Transformer 112 instrument amp. Phono-n-tuner sections are surprisingly robust, too. ... 73s para Sactown
 
Theo A said:
Hello all, my next project is a Yamaha R-50. I am fixing it up for a family member, and when I first inspected the unit, the only issue seemed to be scratchy controls. As long as the buttons weren't moved, it sounded great. All I did was open up the receiver and find the very small holes on the top of the control pots and switches an gave it a good clean. I plug everything back in, and the only input that is giving any sound is the tuner, and even that is very anoemic sounding and quiet. No other inputs work, and I am extemely confused how a simple clean with deoxit could have done anything. What went wrong?
Click to expand...

That is a weird one. After thinking it over, it won't hurt to redo the solder joints for the controls at the front of the main pcb, but that would not explain why only the tuner function is working now. Do you have a CD player or turntable connected to it also? The fact that only the tuner functions would seem to point to the input selector switch, as pointed out by @avionic, but my recollection is that the input selector switches for the R-50 don't carry the signal; they only operate an IC that does the switching. Another possibility is that the solder joints for the input connectors, which are at the back of the main pcb, are cracked, and when you removed the case to spray deoxit, the structure relaxed slightly so that the input connector solder joints are no longer conducting. They are vulnerable to the same thermal cycle fatigue failure mode as those at the front of the board, as they are fixed to both the pcb, and to the back panel. I would check and/or redo the solder joints for the inputs RCA connectors.
 
FRG7SWL said:
Theo A, in addition to Arc de Triamp's suggestions, reflow your voltage regulators, too. Got a Yamaha R-30 receiver last summer off C-List. Seller said it worked last time he played it. Turned on, but that was it. After exploratory exam, noticed voltage regulators were loose. Also replaced replacement 5,600 uf snap-in power caps with radial 10,000 uf Nichicons. IC-amp chip now replicates guitar tones just as well as moi's Peavey Transformer 112 instrument amp. Phono-n-tuner sections are surprisingly robust, too. ... 73s para Sactown
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This was incredibly helpful and it immediately fixed the problem. I appreciate the help, and now I know to check every component on the inside first
 
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